Using Sub Classes (I think that is what im trying to do)

Good day.

Im really new to Qt development but im now getting around nicely. However there are somethings i still find confusing.

Here is an example:
Im writing a database application or rather an application that uses mysql to access data. it works great, i can read write and manipulate data. However now that my program is starting to get bigger, in other words more than 1 Dialog / Widget. Im running to 2 what should be a simple problem.

To create my database connection I use the following call:

Code:

---

createDatabaseConn();

---

and the function is like so

Code:

---

bool createDatabaseConn()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("myhostname");
    db.setDatabaseName("mydatabasename");
    db.setUserName("myusername");
    db.setPassword("mypassword");
    if (!db.open()) {
        //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
        return false;
    }
    return true;
}

---

But know on my second dialog i create the same function. I get an error with something like name already exists so i call the function

createDatabaseConn2 and on the next dialog createDatabaseConn3.

However this is a complete waste in vb.net i would just create a module with the function the from all my forms i would be able to use the function.
So now im trying to do this and this is where im comming into trouble.

i created a c++ class mydatabase.h

with the following :

Code:

---

#ifndef MYDATABASE_H
#define MYDATABASE_H
 
#include <QObject>
#include <QSettings>
#include <QSqlDatabase>
 
class myDatabase : public QObject
{
    Q_OBJECT
public:
    explicit myDatabase(QObject *parent = 0);
 
signals:
 
public slots:
    bool createDatabaseConn();
 
};
 
#endif // MYDATABASE_H

---

in my database.cpp

Code:

---

#include "mydatabase.h"
 
 
myDatabase::myDatabase(QObject *parent) :
    QObject(parent)
{
}
 
 
bool createDatabaseConn()
{
    QSettings settings("ATSTech", "mysettings");
 
    settings.beginGroup("database");
 
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
 
    db.setHostName(settings.value("server").toString());
    db.setDatabaseName("atsadmin");
    db.setUserName(settings.value("databaseUsername").toString());
    db.setPassword(settings.value("databasePassword").toString());
 
    settings.endGroup();
 
    if (!db.open()) {
        //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
        return false;
    }
    return true;
}

---

So now i thought using the connection would be as simple as

Code:

---

#include "mydatabase.h"
 
rm_customer_search::frm_customer_search(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::frm_customer_search)
{
    ui->setupUi(this);
 
    myDatabase::createDatabaseConn();
}

---

And what do you know what a noob i must be i was WRONG.
i get the following error
frm_customer_search.cpp:10: error: cannot call member function ‘bool myDatabase::createDatabaseConn()’ without object

Could someone please let me know what im doing wrong or if im on the compltly wrong track could you let me know what i should be doing .

Regards

Quote:

---

Originally Posted by ShapeShiftme

frm_customer_search.cpp:10: error: cannot call member function ‘bool myDatabase::createDatabaseConn()’ without object

---

This error message does explain the problem very clearly.
You need to create an object first.

Example:

Code:

---

myDatabase myDb;
myDb.createDatabaseConn();
 
// or
myDatabase *myDb = new myDatabase();
myDb->createDatabaseConn();

---

Create -in your MainWindow- only one connection with the database and pass it to every dialog that has to use it.
Something like this:

Code:

---

QSqlDatabase *db = new QSqlDatabase;
db->addDatabase("QMYSQL");
db->...etc...
 
...
myDialog = new MyDialog(this, db);
myDialog->exec();
...

---

Quote:

---

Originally Posted by tbscope

This error message does explain the problem very clearly.
You need to create an object first.

Example:

Code:

---

myDatabase myDb;
myDb.createDatabaseConn();
 
// or
myDatabase *myDb = new myDatabase();
myDb->createDatabaseConn();

---

---

Thnaks very much. Very obvious when someone tells you what you are doing wrong.
And works great